1. Field of the Invention
The present invention relates to an image recording apparatus and a recording head driving method.
2. Description of the Related Art
An image recording apparatus such as an inkjet recording apparatus selectively drives a pressure generator (e.g., a piezoelectric element) provided for each nozzle of a recording head according to image data to thereby cause the nozzle to eject ink, so that an image is recorded on a recording medium such as paper. A known method for driving the recording head that includes the piezoelectric element as the pressure generator is to apply voltage with a common drive waveform to the piezoelectric element associated with each nozzle.
The recording head included in such an image recording apparatus develops unsteady ejection characteristics (e.g., an ink ejection velocity) as affected by the number of nozzles driven at an identical driving timing (hereinafter referred to as a “simultaneously driven nozzle count”), resulting in degraded image quality. A technique has thus been developed to prevent the image quality from being degraded. This technique detects the simultaneously driven nozzle count using the image data and corrects the drive waveform according to the detected simultaneously driven nozzle count, thereby stabilizing the ejection characteristics of the recording head.
Japanese Laid-open Patent Publication No. 2013-199025, for example, discloses a technique that detects the simultaneously driven nozzle count and a nozzle density, calculates a correction value corresponding to the detected simultaneously driven nozzle count and nozzle density, and corrects the drive waveform on the basis of the correction value. Japanese Laid-open Patent Publication No. 2014-200951 discloses another technique that generates in advance a correction value for each of different simultaneously driven nozzle counts, stores the correction values in a data storage, and acquires a correction value corresponding to a detected simultaneously driven nozzle count from the data storage to thereby correct the drive waveform using the correction value.
Each recording head, however, has unique ejection characteristics arising from errors in manufacturing processes, including, for example, variations in capacitance of the piezoelectric element and variations in the size of the nozzle. To record an image on a recording medium using a plurality of recording heads, therefore, simply correcting the drive waveform for driving each recording head uniformly with a correction value corresponding to the simultaneously driven nozzle count does not absorb differences in the ejection characteristics of the recording heads. Degradation of the image quality thus cannot be sufficiently prevented.